Mars and Mercury meet up in the evening sky this month, but the view will be challenging for some northern hemisphere sky watchers, impossible for others. Observers near and south of the equator will get the view. Along the way, Mercury passes 1.7° from Spica on the 2nd. The red planet passes a half-degree from Zubenelgenubi in Libra on the 14th. Mercury is quickly approaching Mars and the two planets will be 2° apart in the center of Libra on the 19th. They’re still close when a waxing crescent moon visits on the 23rd. For those who can see it, the view of Mercury improves until greatest elongation at 23.9° east of the sun on the 29th. By that time, the messenger planet has passed Mars. Mercury will be in the space between Libra and Scorpius.
Part-way up the eastern side of the sky at dusk is Saturn. It’s retrograde all month below the head of one of the Pisces fish. Neptune is nearby. The Great Square of Pegasus is easily noticeable in the region.
Uranus remains slowly retrograde sort of between the Pleiades and Hyades in Taurus. As October begins, the planet rises in late evening. It becomes a mid-evening riser as Earth orbits and the constellations come up earlier.
You can also see Orion and Gemini rising earlier each evening although still late evening to midnight. Jupiter is on the east side of Gemini moving eastward or in direct motion.
And in the dawn, you can see Venus start the month beneath Leo. It enters Virgo on the 9th. Then it passes close to Zavijava on the 12th, Zaniah on the 18th, Porrima on the 22nd, and Theta Virginis on the 28th. It won’t appear nearly as close to Spica when it passes by that star on November 3.
Venus is at perihelion on the 2nd. It will be 0.718 astronomical units from the sun.
Ceres is at opposition on the 2nd. It will be 1.96 astronomical units from Earth. Ceres was the first asteroid discovered, although it’s now designated a minor planet.
Mercury is at aphelion, 0.47 astronomical units from the sun, on the 10th.
Moon’s circumstances
The moon goes north of the equator on the 6th. That’s the same day the moon passes by Saturn and Neptune. Full moon happens the next night. Some people are calling it the first of three “supermoons” this year. The closest full moon of 2025 will be next month, but those in October and December are almost as close. Full moon distance this month is 356,700 km. The moon’s at perigee on the 8th at 359,800 kilometers from Earth. The moon passes by Uranus on the 10th. Northern lunistice is on the 12th at 28.6° from the equator. Last quarter is on the 13th while the moon is close to Pollux and Jupiter. Regulus is visited by the moon on the 16th. Then Luna goes south of the equator on the 18th. It passes Venus the next morning. New moon is on the 21st. A finger-nail moon is near Mars and Mercury on the 23rd and also at apogee at 406,500 kilometers away on the same day. The orange star near the moon on the 25th is Antares. Southern lunistice happens the next day at 28.5° from the equator. The moon’s at first quarter on the 29th.
Meteor showers
The moon is almost new when the Leonis Minorid meteor shower peaks on the 22nd. It’s a minor shower producing perhaps five meteors per hour. Leo Minor is the lesser known lion beneath big bear Ursa Major. This is fairly far north, so it’s mainly a northern hemisphere shower. Far enough north, it’s circumpolar. Otherwise, it’s up closer to dawn in the northeast.
The Orionids meteor shower peaks about the 23rd. The meteors come from dust left behind by Comet Halley. The comet is still almost as far away as it can be, having just gone through aphelion in late 2023, but the dust trails linger throughout the orbit. Earth is going one way and the comet bits the other, so the meteors move very fast. They’re also dim, but they leave persistent trains that can glow for several seconds. You may see up to 20 per hour. And with the shower happening when the moon is new, moonlight won’t be a limiting factor.
With two meteor showers peaking around the same time, you may wonder how to know which one a particular meteor came from. Try to trace it back to the constellation. Leo Minor and Orion are far enough apart you shouldn’t have much trouble with that. Of course, there’s always the chance you’ll see a random meteor that doesn’t seem to come from either.
Jupiter moon shadow events
A series of double shadow events on Jupiter began last month. Viewing in big enough telescope, you may see two shadows from Jupiter’s moons on the planet’s disk from time to time. The following times were predicted with the International Occultation Timing Association’s WinOccult program. In a few cases, other services predict start or end times varying by one or more minutes. Start watching about five minutes early and plan to keep watching about five minutes later.
October 4 6:49 to 8:16 Europa, Io
October 6 1:17 to 1:29 Ganymede, Io
October 7 19:45 to 21:34 Europa, Io
October 11 8:42 to 10:52 Europa, Io
October 13 3:10 to 5:24 Ganymede, Io
October 14 21:38 to 23:52 Europa, Io
October 18 10:41 to 12:49 Io, Europa
October 18 13:04 to 13:29 Ganymede, Callisto
October 20 6:23 to 7:17 Io, Ganymede
October 21-22 23:59 to 1:45 Io, Europa
October 25 13:17 to 14:42 Io, Europa
October 29 2:35 to 3:39 Io, Europa
November 1 15:53 to 16:35 Io, Europa